Alkyl, benzylic and allylic bromides are fundamental building blocks that can be used in a wide range of transformations of both practical and historical significance. In spite of this, setting the stereochemistry of a halogen-bearing carbon remains challenging. A great deal of research has focused on asymmetric α-halogenation of carbonyls and amino-halogenations of olefins. However, these techniques rely heavily on stoichiometric sources of chirality in the form of chiral auxiliaries or chiral brominating agents. To date, the catalytic systems that set the stereochemistry of a halogen-carbon bond, with the exception of halolactonizations, are sparse. Furthermore, to the best of our knowledge, enantioselective hydrobrominations of olefins have not been reported. Accordingly, new methods for the efficient and enantioselective hydrobrominations of olefins would provide more efficient and economical access to a variety of important synthetic building blocks, including drug intermediates and chiral phosphines.
Additionally, chiral, non-racemic phosphines are crucial components in a multitude of important enantioselective transformations, including asymmetric Diels-Alder reactions, hydroformylations, aldol reactions, aminations, hydrogenations, hydrosilylations, conjugate additions and other carbon-carbon bond formations. However, the syntheses of enantioselective phosphine ligands often require multiple steps, including chiral resolutions to separate enantiomers. The lack of general and flexible approaches to asymmetric phosphines is often reflected in their price, which can rival the cost of precious metal portion of the catalyst. Accordingly, there is a need for new, efficient, and enantioselective methods for the preparation of chiral phosphines and related compounds, and well as methods for the preparation of intermediates for the preparation of such compounds.